OSCORE Appendix B.2 CBOR CVE-2026-29013

| EUVD-2026-23535 HIGH
Out-of-bounds Read (CWE-125)
2026-04-17 VulnCheck
8.8
CVSS 4.0
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CVSS VectorNVD

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

2
Re-analysis Queued
Apr 20, 2026 - 17:52 vuln.today
cvss_changed
Analysis Generated
Apr 18, 2026 - 00:18 vuln.today

DescriptionNVD

libcoap contains out-of-bounds read vulnerabilities in OSCORE Appendix B.2 CBOR unwrap handling where get_byte_inc() in src/oscore/oscore_cbor.c relies solely on assert() for bounds checking, which is removed in release builds compiled with NDEBUG. Attackers can send crafted CoAP requests with malformed OSCORE options or responses during OSCORE negotiation to trigger out-of-bounds reads during CBOR parsing and potentially cause heap buffer overflow writes through integer wraparound in allocation size computation.

AnalysisAI

Out-of-bounds read in libcoap's OSCORE CBOR parsing can escalate to heap buffer overflow, enabling remote unauthenticated attackers to trigger memory corruption via malformed CoAP packets. Affects libcoap versions prior to v4.3.5b. …

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RemediationAI

Within 24 hours: inventory all systems and applications using libcoap and document current version numbers. Within 7 days: test and deploy libcoap v4.3.5b or later across all development, staging, and production environments; prioritize IoT devices and constrained network endpoints. …

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CVE-2026-29013 vulnerability details – vuln.today

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